Table of Contents

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  1. Preface
  2. Using the Designer
  3. Working with Sources
  4. Working with Flat Files
  5. Working with Targets
  6. Mappings
  7. Mapplets
  8. Mapping Parameters and Variables
  9. Working with User-Defined Functions
  10. Using the Debugger
  11. Viewing Data Lineage
  12. Comparing Objects
  13. Managing Business Components
  14. Creating Cubes and Dimensions
  15. Using the Mapping Wizards
  16. Datatype Reference
  17. Configure the Web Browser

Saving Previous Values

Saving Previous Values

When you step through the Slowly Changing Dimensions Wizard, you choose the columns in which you want to detect changes. The Designer creates an additional column for each column you select and names the additional column after the original, PM_PREV_
ColumnName
. The Integration Service uses these columns to store previous dimension values.
When the Integration Service writes a new dimension to the target, the
previous
columns remain null. Each time the Integration Service updates a dimension, it writes existing data into the corresponding
previous
column, and then writes updates into the original column. As a result, each row in a Type 3 Dimension target contains current dimension data. Each row also contains the previous versions of dimension data, if the dimension has changed.
For example, the first time the Integration Service writes the following dimensions to the target, the
previous
column, PM_PREV_STYLES remains null:
PM_PRIMARYKEY
ITEM
STYLES
PM_PREV_STYLES
6345
Sock
20
-
6346
Boot
25
-
When the Integration Service updates these rows, it writes the values in the STYLES column (20 and 25) into PM_PREV_STYLES, and then replaces the style data with new style data (14 and 31):
PM_PRIMARYKEY
ITEM
STYLES
PM_PREV_STYLES
6345
Sock
14
20
6346
Boot
31
25


Updated July 02, 2020